How To Buy Electrical Boxes

Electrical boxes, also known as junction boxes, enclose wire connections to protect against short circuits, which can cause fires. This guide describes the different types of electrical boxes, their materials and applications so you can feel confident you’re choosing the right box for your project.

Important: The National Electrical Code (NEC) and local building codes regulate the types of electrical boxes that can be used in specific applications, as well as the manner of installation. These codes require that electrical boxes not be covered with drywall, paneling or other wall coverings, but with electrical box covers that can be matched to all boxes. Check with your local building inspector before you start any electrical project and be sure to obtain required permits. When your work is complete, always have it inspected for compliance with local codes to ensure that it has been safely installed.

Types of Electrical Boxes

Specific boxes are designed for use indoors or outdoors, while others are made to be installed behind or outside of walls.

Tip: Code requires that all electrical boxes be fitted with box covers. Exterior covers need to be watertight.

Handy box

• Mounts on the surface of a wall
• Can contain light switches or receptacle
• Ideal for areas where behind-the-wall installation is difficult or not possible

Junction box

• Wires connect only to each other, never to a switch, receptacle or fixture
• Allows circuits to be safely split and branched into different directions

New work box

• Installed as part of a new construction project
• Mounts directly to studs or joists, or placed between two studs using a bar hanger before drywall is applied

Old work box

• Also called “remodeling box”
• Designed to be installed on drywall after it has been hung
• Has clamps built in to the box
• Ideal for adding new outlets to pre-existing walls

Outdoor box

• Available in metal and nonmetallic units
• Protects wiring from the elements with gaskets, sealed seams, and watertight covers

Shapes and Sizes

The shape of an electrical box can help you identify its purpose.

Standard rectangular box

• Most common electrical box
• Houses a single electrical switch or outlet

Square box

• Also called “double-gang box”
• Houses two devices, either a combination outlet/switch or pair of outlets/switches in one location

Round or octagonal box

• Houses lightweight fixtures or safety devices in ceiling such as a light or smoke and carbon monoxide alarms

Ceiling box

• Used for heavier fixtures, such as ceiling fans or chandeliers
• Choose one that is specifically designated to support extra weight

Materials

Electrical boxes are constructed of either metallic material, such as aluminum, steel or cast iron, or nonmetallic material, such as PVC or plastic.

Metal boxes

• Many local building codes require metal junction boxes because they are durable and ensure long-lasting performance
• Should be used for exposed indoor applications, such as with conduit in an unfinished basement

Plastic or PVC boxes

• Inexpensive, easy-to-install
• Can be placed behind drywall
• Should only be used with nonmetallic cable

Installation Tips and Tricks

Always check with your local building inspector before starting any electrical project to ensure that you are following code.

For new construction installations, diagram the room and be sure you have enough electrical boxes to accommodate all the light switches, outlets and fixtures you need.

When working in finished areas, use a stud finder to locate studs and make sure they don't interfere with the placement of a new box.

Trace an outline of the box on the wall where it will be installed to mark cutting lines. Utility knives work well for cutting holes in drywall, keyhole saws are good for plaster, and saber saws are useful for wood.

Light switches are generally installed about 42 inches from the floor.